JPS60212100A - Digital speaker - Google Patents

Abstract

PURPOSE:To improve a space ratio and magnetic utilizing factor by improving a voice coil of a multi-voice coil system (MVC system). CONSTITUTION:A voice coil is formed by plural winding parts consisting of rectangular wire different in thickness and having the same width. At this time, 1st, 2nd, 3rd and fourth bit winding parts 15-18 are constituted of rectangular factor with the same width, and numbers of turns of these winding parts are 1, 2, 4 and 8-turn respectively, the thickness being in proportion to each number of turns. Each winding part is fitted in such condition where each outer diameter is same and the winding parts are brought into close contact each other with respect to a voice coil bobbin 8. The homonization of impedances from 1bit-n- bit is performed by means of the thickness of the rectangular wire and each winding outer diameter is made same. Furthermore the waste between winding parts is avoided, and the accuracy of the outer-most diameter can be improved, thereby the reduction of a magnetic gap can be possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a digital speaker that can directly input a digital signal and obtain an analog audio output.

(Conventional structure and its problems) A digital speaker is a device that directly inputs a digital signal (pulse) to obtain a conventional analog sound output. The pulse having the sampled value is applied to a speaker and subjected to D/A conversion. Electrodynamic speakers essentially have a D/A conversion function, and many digital speakers have been developed using this function.

For this D/A conversion, it is necessary to have an acoustic output value that corresponds to all sample values of the input pulse.
For a signal system having a pulse of maximum n bits, it is necessary to weight the output of the speaker up to 2n-1. For example, an 8-bit signal system requires an output change from a minimum value of 2° (=1) to a maximum value of 2' (=128).

For this purpose, a multi-unit method uses a total of n units with weights corresponding to each bit to synthesize sound in space, and the speaker driving force F=BfiI(B
:Magnetic flux density, Q=Voice coil effective winding length. ) is weighted by the magnetic flux density B in the excitation type magnetic circuit as [
A method in which weighting is performed based on the voice coil effective winding length Ω is generally called a "multi-voice coil method."

The present invention utilizes the multi-voice coil method (hereinafter referred to as MVC) described above.
Abbreviated as method. ).

FIG. 1 shows an example of a speaker structure based on the conventional MVC method, and shows an example in the case of 4 bits.

In the figure, 1 is a lower plate, 2 is a center pole, 3 is a magnet, 4 is an upper plate, 5 is a frame, 6 is a cone diaphragm, 6a is an edge, 7 is a gasket, 8 is a voice coil bobbin, 9 is a suspension, 10 is the dust cap, 11 is the l bit winding part, 12.13 and 1
4 are winding portions of the 2nd bit, 3rd bit, and 4th bit, respectively.

Here, independent wire rings each having a weight are wound around the voice coil bobbin 8, and the 1st bit winding section 11 starts with 1 turn, and the 4th bit winding section 14 starts with 23 (=8 ) has become a turn. In addition, each of these windings needs to have the same impedance, so 1 bi
The tth winding part 11 is extremely thin and has 4 bits which is the final bit.
The eye winding portion 14 uses the largest wire rod.

FIG. 2 shows a half cross section when the space factor of each winding section 11 to 14 applied to the voice coil bobbin 8 in FIG. 1 is maximized. When using the voice coil as shown in FIG. 1, Even if the most rational winding method is used, the state shown in Fig. 2 will result, resulting in a voice coil with a very poor space factor. A wide magnetic gap A is required between the two, resulting in a large loss of magnetic energy.

(Objective of the Invention) The present invention is intended to solve the above-mentioned problems, and aims to provide a digital speaker that improves the space factor by improving the voice coil of the MVC method and improves the magnetic utilization factor. That is.

(Structure of the Invention) The present invention has a plurality of winding parts made of rectangular wires having the same width and different thicknesses, and the number of windings for each winding part is 2n.
(n = 1, 2, 3, 4...), and the thickness increases sequentially at the same time, each independently on the same bobbin. The voice coil has a single-layer winding arranged in the axial direction in close contact with each other, each winding portion having the same outer diameter, and a constant impedance.

(Description of Embodiment) FIG. 3 is a half-sectional view of the voice coil of an embodiment of the MVC digital speaker of the present invention, where 8 is the voice coil bobbin, 15, 16, 17, and 18 are the first bits, respectively.
, the second bit, the third bit, and the fourth bit.

Each of the winding parts 15 to 18 according to the present invention is composed of a rectangular wire having the same width, and the 1st bit winding part 15 has one turn and is the thinnest, and the 2nd bit winding part 16 has 2 turns. The thickness is twice that of the winding part 15, the 3rd bit winding part 17
has 4 turns and is 4 times as thick as the winding section 15. The 4th bit winding section 18 has 8 turns and is 8 times as thick as the winding section 15. Each winding section 15 to 18 is attached to the voice coil bobbin 8. On the other hand, they have the same outer diameter and are attached in close contact with each other without any gaps.

FIG. 4 is a circuit example showing an example of an input signal system of an MVC digital speaker, where ■ indicates the first bit signal input terminal, ■, ■, and ■ indicate the second, third, and fourth bit input terminals, respectively. 19 to 22 are changeover switches, switches 19 to 22
When is OFF, the bit pulse is OFF; when a, the positive direction pulse is ON; when b, the negative direction pulse is ON.

In the figure, 15A to 18A and 15B to 18B indicate power supplies.

Figure 5 shows an example of a simpler input signal system than Figure 4. When switches 27 to 30 are OFF, the pulse of that bit is OFF, and when the switch is ON, the pulse is ON only in the positive direction. It shows. In the figure, 23-26
indicates power supply.

(Effects of the Invention) As explained above, the present invention has the following advantages:
The thickness of the rectangular wire is used to equalize the impedance up to the nth bit, making the outer diameter of the windings the same, and making sure that the wires are in close contact with each other without any gaps, thereby eliminating waste between the windings and making the outermost diameter By increasing the precision of the magnetic field, it is possible to narrow the magnetic gap, thereby contributing to improving the efficiency and magnetic utilization of MVC digital speakers. It has the advantage of being highly practical and highly practical.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of a speaker structure using the conventional MVC system, Figure 2 is a diagram showing an example in which the space factor of the winding section applied to the voice coil bobbin in Figure 1 is maximized, and Figure 3 is a diagram showing the structure of this speaker. FIG. 4 is a diagram showing an example of a signal system of the invention; FIG. 5 is a diagram showing an example of an input signal system simpler than FIG. 4. . 1... Lower plate, 2... Center ball, 3
... Magnet, 4 ... Upper plate, 5
... Frame, 6 ... Cone diaphragm, 7.
...Gasket, 8 ...Voice coil bobbin, 9
...Suspension, 1o...Dust cap,
15... 1st bit winding part, 16... 2nd bit winding part, 17... 3rd bit winding part, 1
8... 4th bit winding part. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A plurality of winding portions made of rectangular wires having the same width and different thicknesses are arranged so that the number of turns for each winding portion is 2n (n=1.
2, 3, 4.・・・・・・・・・), the thickness of each bobbin increases while satisfying the following relationship, and the thickness of each bobbin gradually increases. A digital speaker characterized by having a voice coil with the same diameter and constant impedance.